science-astronomy: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/science-astronomy - from package: science-astronomy

You may install the required package with command apt-get install {package}

Error in other languages:
science-astronomy: bevel nie gevind nie
science-astronomy: comandă negăsită
science-astronomy: comando não encontrado
science-astronomy: commande introuvable
science-astronomy: command not found
science-astronomy: käsku ei ole
science-astronomy: không tìm thấy lệnh
science-astronomy: komanda nerasta
science-astronomy: Kommando nicht gefunden.
science-astronomy: kommandot finns inte
science-astronomy: komut yok
science-astronomy: nie znaleziono polecenia
science-astronomy: níor aimsíodh an t-ordú
science-astronomy: no se encontró la orden
science-astronomy: no s'ha trobat l'ordre
science-astronomy: opdracht niet gevonden
science-astronomy: parancs nem található
science-astronomy: perintah tidak ditemukan
science-astronomy: príkaz nenájdený
science-astronomy: příkaz nenalezen
science-astronomy: команда не найдена
science-astronomy: командата не е открита
science-astronomy: 命令找不到
science-astronomy: コマンドが見つかりません